Conventionally, in the case where construction with glass is carried out in a place requiring sound insulation such as windows, a method in which a sound insulating effect is increased by increasing the thickness of the glass to increase the weight, or a method in which a sound insulating effect is increased by using a laminated glass in which two or more glass plates and an interlayer film are laminated has been carried out. In the latter method using an interlayer film, the sound insulating properties of the glass are improved by the damping performance of the interlayer film and the performance of the interlayer film for converting vibrational energy to thermal energy.
As a method for improving the sound insulating properties, an interlayer film in which a copolymer of polystyrene and a rubber-based resin is laminated with a plasticized polyvinyl acetal-based resin has been proposed (see, for example, PTL 1).
Further, an interlayer film for laminated glass and a laminated glass which are composed of polyvinyl butyral and have certain impact resistance and sound insulating properties have been proposed (see, for example, PTL 2).
As a method for producing a laminated glass having favorable sound insulating properties, a method for producing a laminated glass including forming an interlayer film having a three-layer structure by sandwiching a layer containing a copolymer of styrene and a rubber-based resin monomer between layers containing a thermally adhesive resin and laminating the interlayer film with two or more glasses (see, for example, PTL 3 or PTL 4) and a method for producing a laminated glass using a laminate having improved adhesiveness between layers by laminating a layer A containing a polyvinyl acetal and a layer B containing a polyolefin (see, for example, PTL 5) have been proposed.
Further, recently, from the viewpoint of energy saving, the improvement of fuel efficiency of cars and the like has become a bigger issue.